Relative Abundance of the Spotted Tentiform Leafminer, Phyllonorycter blancardella (F.), and the Apple Blotch Leafminer, P. crataegella (Clemens) (Lepidoptera: Gracillariidae), on Sprayed and Unsprayed Apple Trees in Connecticut

Abstract

The relative abundance of Phyllonorycter blancardella (F.) and P. crataegella (Clemens) was examined on sprayed and unsprayed apple trees in Connecticut by identifying pupae collected from fallen leaves during the third leafminer generation of 1980–1982. P. crataegella dominated at eight of nine sprayed sites. By contrast, P. blancardella dominated at seven of eight unsprayed sites. The widespread occurrence of P. blancardella on apple trees and especially its dominance in one sprayed orchard contradicts published reports on its absence in Connecticut. Temporal and spatial variation in species composition at unsprayed sites is attributed partly to defoliation by the gypsy moth, Lymantria dispar (L.), and to the proximity of potential colonists in commercial orchards. Dominance of P. crataegella in most commercial orchards is probably related to its resistance to insecticides. The cause of P. blancardella dominance at most unsprayed sites is unknown.